focus problem


Status
Not open for further replies.
Nov 21, 2004
85
0
6
#1
i used my 50mm on my friend's dslr.

when i half-press the shutter release to focus, the view from the viewfinder is blur although the camera tells me focus is locked and good. then, when i press to shoot, the image came out to be good and in focus. :dunno:

i tried again, this time when the camera tells me focus is locked (although the view is still blur), i moved my body back abit til the subject in the viewfinder is sharp. i press the shutter to take the pic. this time the image recorded is blur, although the viewfinder is sharp. :dunno:

i tried manual focus. same thing, sharp in viewfinder, but when i shoot, the resultant image is blur.

whats going on? back/front focus?
when i use this lens on my own dslr, its good.
my lens bad? or his cam bad?

thanks guys
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#4
olsomica said:
i used my 50mm on my friend's dslr.

when i half-press the shutter release to focus, the view from the viewfinder is blur although the camera tells me focus is locked and good. then, when i press to shoot, the image came out to be good and in focus. :dunno:

i tried again, this time when the camera tells me focus is locked (although the view is still blur), i moved my body back abit til the subject in the viewfinder is sharp. i press the shutter to take the pic. this time the image recorded is blur, although the viewfinder is sharp. :dunno:

i tried manual focus. same thing, sharp in viewfinder, but when i shoot, the resultant image is blur.

whats going on? back/front focus?
when i use this lens on my own dslr, its good.
my lens bad? or his cam bad?

thanks guys
Do the lines/grids/features (if any) on the focusing screen appear clear? If they are, then the calibration of the SLR may be out.
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#7
espn said:
Confirm dioptre adjustments.
But manual focus can become sharp leh? If diopter wrong, I don't think it will become sharp at all.
 

espn

Deregistered
Dec 20, 2002
21,905
0
0
Planet Nikon
#10
lsisaxon said:
Walao.. mai suan lah.. Just an opinion only leh... I may be wrong..
I also ma.. opinion nia... newbie lah... don't take it to heart, just joshing ar'd ;)
 

Nov 21, 2004
85
0
6
#12
confirm not diopter
adjusted max bothways still like that
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#13
espn said:
I also ma.. opinion nia... newbie lah... don't take it to heart, just joshing ar'd ;)
Dunno leh.. if my diopter wrong, image will never be sharp however I focus one leh.. :dunno:
 

Nov 21, 2004
85
0
6
#14
lsisaxon said:
But manual focus can become sharp leh? If diopter wrong, I don't think it will become sharp at all.
true true
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#16
olsomica said:
true true
Which camera body is that? Can you try something? Use AF, focus on a marking on a ruler placed 45 degrees, then see if the focus on the viewfinder is in front or behind the AF point.
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#17
olsomica said:
confirm not diopter
adjusted max bothways still like that
should be somewhere in between.


olsomica said:
i used my 50mm on my friend's dslr.

when i half-press the shutter release to focus, the view from the viewfinder is blur although the camera tells me focus is locked and good. then, when i press to shoot, the image came out to be good and in focus. :dunno:

i tried again, this time when the camera tells me focus is locked (although the view is still blur), i moved my body back abit til the subject in the viewfinder is sharp. i press the shutter to take the pic. this time the image recorded is blur, although the viewfinder is sharp. :dunno:

i tried manual focus. same thing, sharp in viewfinder, but when i shoot, the resultant image is blur.

whats going on? back/front focus?
when i use this lens on my own dslr, its good.
my lens bad? or his cam bad?

thanks guys
Common sense will tell your that nothing wrong with the lens, and the camera focusing system, just only the dioptre adjustments, or your friend modified it for his/her eye only.
 

espn

Deregistered
Dec 20, 2002
21,905
0
0
Planet Nikon
#18
catchlights said:
should be somewhere in between.



Common sense will tell your that nothing wrong with the lens, and the camera focusing system, just only the dioptre adjustments, or your friend modified it for his/her eye only.
:thumbsup:
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#19
espn said:
:thumbsup:
Taking D70 as an example, there are 2 screws you can turn for adjusting the mirror stop position. One of them adjusts the stopper for the mirror for the AF sensor and the other adjusts the stopper for the mirror to the focusing screen. A possibility is that either the mirror is jammed or it wasn't calibrated correctly.

The D70 which my previous company bought has both alignment slightly off. By shooting a 45 degree ruler, I was able to see that what was focused by the AF sensor, the focusing screen and the CCD are off by a bit.

Using a microscrope (previous company was dealing with semiconductors), I was able to precisely calibrate the optical distances of the AF sensor, focusing screen and the CCD sensor by using the 2 stopper screws. And it does make quite a difference on the focusing accuracy.
 

lsisaxon

Senior Member
Nov 29, 2004
11,941
0
0
#20
roti_prata said:
he where got say mf is sharp?
Let me rephrase that.. If diopter is wrong, the viewfinder image can never be sharp. But he was able to focus and obtain a sharp image in the viewfinder, which means that the diopter should be correct. However, getting the image sharp in the viewfinder did not yield a sharp image in the sensor, which also means that the distance from the lens mounting flange to the focusing screen is not the same as the distance from the lens mounting flange to the sensor. If it were really the diopter, everything else in the viewfinder would not be sharp also.
 

Status
Not open for further replies.
Top Bottom